Vitamin C, also known as L-ascorbate, being a water-soluble vitamin is unstable in an aqueous medium. Thus, water-based cosmetic formulations including Vitamin C as a component are typically not stable. Eliminating water from the formulation cures this problem.
Currently produced and stable non-aqueous Vitamin C products contain either waxes or combinations of waxes and oils to promote stability of the suspensions but leave an oily or waxy residue on the skin after use which is unappealing and unaesthetic. In general aqueous formulations containing modifications of Vitamin C have proven either very expensive or otherwise limiting to the commercialization of a Vitamin C containing consumer product.
Vitamin C has been shown to be beneficial to the skin when used in formulae such as "Citrix", which is an oil-wax suspension. This formulation has aesthetic problems in that it leaves a greasy coating on the skin. However, it does provide an occlusive coating on the skin which allows the vitamin to hydrate in the skin's own moisture, and which also enhances the delivery of the vitamin.
The invention formulation utilizes a liquid suspending medium and other beneficial agents to eliminate the aesthetic problems seen with all other oil-wax suspensions. It also has the following properties/characteristics: faster penetration into the skin due to the presence of low molecular weight lipids; presence of protective agents such as grape seed oil; improved hydrophobic barrier such as PMMA beads FHC (perfluoropolymethyl isopropyl ether--tradename: FOMBILIN-HC available from Ausimont SpA); non greasy feeling due to the volatile hydrocarbon base and a wax-free formulation. The invention provides a unique formulation having these characteristics and as also provides a stable form of Vitamin C for delivery to the skin.
In general, formulations containing ascorbic acid are known in the art. For example, U.S. Pat. No. 5,561,158 to Yu et al. discloses compositions containing 2-hydroxycarboxylic acids and related compounds including ascorbic acid, that are applied to the skin to alleviate or improve skin lines, botches, blemishes, nodules, wrinkles, etc. Yu et al. discloses further that the 2-hydroxycarboxylic acids and their related compounds are "dissolved" in a solution prepared from ethanol, water, propylene glycol, butylene glycol, acetone or other pharmaceutically acceptable vehicle.
Another example is U.S. Pat. No. 5,122,536 to Perricone which discloses a method for the therapeutic treatment of psoriasis in which ascorbic acid, or a precursor of derivative thereof, is topically applied to the affected skin areas. In the Perricone compositions the ascorbic acid is provided in the form of the acid per se or in the form of a precursor or derivative. Suitable carriers include water, alcohols, oils and the like chosen for their ability to "dissolve or disperse" the active ingredient.
Still another example of compositions which include ascorbic acid is described in U.S. Pat. No. 4,938,969 to Schinitsky et al. Schinitisky et al. discloses a composition for reducing wrinkles by applying a topical formulation containing ascorbic acid, tyrosine and a non-toxic zinc salt. These formulations are incorporated into a tissue compatible vehicle such as hydrophilic lotion, ointment, cream, or gel-based vehicles. Examples of such vehicles are commercially available as "Dermabase" and "Unibase" formulations.
As described in the representative art, formulations containing ascorbic acid for use in various skin applications are shown. However, in the compositions described in Yu et al. and Perricone patents the ascorbic acid component is "dissolved" in an aqueous vehicle and in the Schinitsky patent the ascorbic acid is combined with tyrosine and a non-toxic zinc salt.
Advantage of the present invention over the known art is in the delivery system of Vitamin C to the skin. As previously mentioned, it is known that Vitamin C is not stable in water or in water-based cosmetic formulations. Surprisingly, the non-aqueous vehicle of the invention suspends anhydrous, particulate Vitamin C so that it can be applied in the manner similar to water containing lotions. In addition, the present composition, preferably, does not contain waxes, oils or silicone materials thus when it is applied to the skin it evaporates from the skin without leaving a waxy or oily residue left behind.
Thus it is an object of the invention to provide a means of dispensing Vitamin C in a liquid vehicle that embodies the desirable properties of formulations in which Vitamin C is not stable. The formulation of the present invention provides a non-aqueous viscous liquid that suspends the insoluble Vitamin C. The formulation is applied to the skin in a manner similar to water containing lotions and evaporates from the skin following application and leaves no waxy residue. The formulation is preferably wax, oil and silicone free, but these components may be included as optional ingredients. A preferred formulation is comprised of ascorbic acid, a volatile organic solvent and a gelling base.
The advantages of this invention over the prior art is that the application of the ascorbic acid (Vitamin C) is provided in a non-waxy, viscous liquid with adequate suspending ability so as to provide vitamin stability with long term uniform dosage of the Vitamin C.